The main purpose of this research is to continue an ongoing longitudinal study of mental and social development of a cohort of children observed from 2 months to 4 years. The premise of this research is that learning in childhood occurs primarily within an interpersonal context; thus, a central goal is to describe bow diverse infant and maternal behaviors relate to central dimensions of children's social and mental competencies. Children participating in the assessment constitute a longitudinal cohort seen first at 2, 5, 13, and 20 months of age, and finally in a follow-up at 4 years. Major objectives of this longitudinal research are to study stability, continuity, and interaction in mental, social, and emotional development in the first years of life. One notable aspect of the follow-up is a test of materials based on the curriculum-oriented Project Spectrum, organized between the Harvard University School of Education, the Eliot-Pearson Department of Child Study at Tufts University, and the CFRS. Project Spectrum is unique in the United States for its development of a curriculum that goes beyond IQ to assess a wide range of preschool children's interests and capabilities. The 'multiple intelligences' that Project Spectrum's procedures assess include natural science ability, bodily-kinesthetic skills, musical talents, distinctive styles of work, as well as linguistic and logical-mathematical abilities. Because traditional psychometric measures of intelligence at this age typically sample from a narrow range of mental abilities, such measures are limited in terms of the information they provide about the possible relevance of antecedent variables, and they are also restricted in terms of the outcome variables they successfully predict. In contrast, the Project Spectrum Field Assessment Battery samples from a wide range of preschoolers' capabilities and interests and thus affords richer opportunities to respond to many theoretical and pragmatic questions that surround the central issue of stability in mental development.